The present invention relates to security control systems and in particular to a security control system that combines wireless communication and communication over the existing power lines in a building or dwelling.
Most conventional security systems fall into two main categories: wireless and hard-wired. The wireless systems typically employ ultrasonic or radio frequency signals to communicate information from entry sensing devices to central alarms. While such systems generally possess the inherent advantage of easy installation, wireless security systems tend to be plagued by a relatively high percentage of false alarms. This is due in large part to the congested state of the airways. In addition, because radio frequency signals pass readily through walls of buildings and homes, the possibility of a system in one building falsely triggering a system in an adjacent building is greatly increased. In this regard, it must be borne in mind that even a relatively low false alarm rate of once every several hundred hours of use may be sufficient to cause a loss of confidence in the reliability of a system.
Hard-wired systems, on the other hand, are generally more reliable and less subject to false triggering. However, hard-wired systems require the installation of a separate, dedicated wiring system, which for most consumers, renders such systems prohibitively expensive.
Accordingly, it is the primary object of the present invention to provide an improved security control system that is reliable, relatively inexpensive, and simple to install.
In addition, it is an object of the present invention to provide an improved security control system that utilizes wireless audio communication and power line communication to facilitate system installation.
Moreover, it is an object of the present invention to provide a security control system that also provides the ability to remotely control the operation of various loads, including lights and appliances.
Furthermore, it is an object of the present invention to provide an improved security control system that cannot be readily defeated by an intruder and yet is easily disarmed following an authorized entry.
In general, the security control system according to the present invention comprises: an entry detector, a signal relay module, a controller, and a slave module. The entry detector is battery powered and adapted to be mounted at each door and window of a home or building. Upon the opening of a protected door or window, a coded audible signal is emitted by the entry detector. The coded audible signal is received either directly by the controller if located within sufficiently close proximity to the activated entry detector, or by a signal relay module. The signal relay module is adapted to be plugged into a conventional wall outlet and is intended to be placed in each room or area of the home or building in which an entry detector is located. Only one signal relay module is required in each room or area, regardless of the number of entry detectors located in the room or area. The function of the signal relay module is to receive the coded audible signal emitted by the entry detector and transmit in response thereto a digital pulse coded signal over the power lines to the controller. The controller is also adapted to be plugged into a convention wall outlet and is adapted to receive and transmit digital pulse coded signals over the power lines, in addition to being able to receive coded audible signals directly from an entry detector as previously mentioned. In response to the receipt of a signal either directly from an entry detector or from a signal relay module, the controller is adapted to transmit a digital pulse coded alarm signal over the power lines to the slave modules. The slave modules are similarly plugged into the wall outlets and serve to control the actuation of various loads, such as an alarm, siren, or lamp, or control the performance of a specified task, such as a telephone dialer. In addition, the controller can selectively address individual slave modules to provide a user with the ability to remotely control the actuation of lights and appliances, or other such loads. Thus, the controller according to the present invention allows the system to function as a security system or as a remote control system.
When operated as a security system, the present system provides two basic modes of operation: INSTANT-ARMED and ARM-DELAY. In the INSTANT ARMED mode, the cntroller is programmed to activate an internal alarm and transmit an alarm signal to the slave modules to immediately actuate the alarm devices upon the receipt of an intrusion signal. This mode of operation is intended to be used, for example, when a home is occupied at night and the homeowner desires to be instantly notified of an attempted unauthorized intrusion. The ARM-DELAY mode, on the other hand, is used when setting the system before leaving the protected premises, so that upon return the owner is provided with a predetermined time period subsequent to re-entry in which to enter a secret disarm code into the controller to inhibit actuation of the alarm. Unlike conventional security systems in which this delay function is implemented at the controller, in the present system the time delay function is contained within the remotely located slave modules. More particularly, when in the ARM-DELAY mode, the controller is programmed upon receipt of an intrusion signal to transmit a coded signal over the power lines to the remotely located slave units which is effective to initiate a digital timer in each slave unit. Once initiated, the slave units will automatically activate their respective loads or perform their respective tasks upon expiration of the predetermined delay period unless a disarm signal is received over the power lines from the controller. The controller is programmed to transmit this disarm signal only upon entry of a secret user-selected code. Accordingly, it will be appreciated that the present system cannot be defeated by a burglar simply disconnecting or disabling the controller within the time delay period provided in the ARM-DELAY mode.
An additional significant feature of the present security control system consists of the unique coded audio communication link between the entry detectors and the signal relay modules and controller(s). In the preferred embodiment, the coded audible signal transmitted by an entry detector upon detection of an intrusion event comprises alternating 6 KHz and 7.3 KHz tone bursts with predetermined spacing between successive tone bursts to eliminate echo problems. The selection of the particular frequencies used in the coded audio link is based primarily on the following considerations: (1) audible signals provide the owner with a measure of assurance that the entry detector/transmitters are functioning properly, (2) the use of signals in the audible frequency range significantly reduces the possibility of one system falsely triggering adjoining systems, and (3) the relatively low degree of natural occurrence of the frequencies.
The audio receivers in the signal relay modules and in the controller function in accordance with the Constant False Alarm Rate ("CFAR") principle to effectively isolate the coded signal from background noise and thereby predictably control the probability of false alarms and provide a predictable signal-to-noise ratio. The audio receivers also include unique decoding circuitry which utilizes the exclusion principle by sequentially looking for the simultaneous presence of the 6 KHz tone and the absence of the 7.3 KHz tone followed by the simultaneous presence of the 7.3 KHz tone and the absence of the 6 KHz tone. The result of these combined features is a highly reliable audio communication link that virtually eliminates the possibility of false alarms.
Also of significance to the security control system according to the present invention is the power line communication technology used to reliably transmit information between the signal relays, controller, and slave modules. Information between the relay, controller, and slave modules is communicated over the power lines by impressing a relatively high frequency (e.g., 121 KHz) carrier signal onto the power lines. The transmitted messages are in digital pulse coded form with individual binary data bits being represented by a carrier frequency burst or "pulse" that is generated during predetermined periods of the 60 Hz AC waveform. Specifically, a binary "1" is represented by a pulse produced during the first half of the 60 Hz AC waveform and a binary "0" is represented by a pulse produced during the second half of the AC waveform. Thus, synchronization between the various units is achieved by synchronizing the transmission and receipt of the digital pulse coded signals to the 60 Hz AC waveform. In addition, in the preferred embodiment of the present invention the signal relay modules and controllers are microprocessor-based and include programmed algorithms for checking the AC power line prior to transmission of a message to determine if another device is already transmitting a message or if there exists an unacceptable level of noise on the AC power line which would preclude the reliable transmission and receipt of a message. If either the presence of intelligence or an unacceptable noise level is detected, the devices are programmed to execute a randomly generated time delay before retransmission is attempted. In this manner, the potential priority conflict over power line access is resolved and the likelihood of two devices creating a perpetual standoff condition is avoided.
To prevent the present security control system from being rendered imoperable by the loss of AC power, the units in the system which rely mainly upon AC power--namely the signal relay, controller, and certain of the slave units--are each provided with battery backup power which is automatically enabled when primary AC power is lost. These units also include internal quartz crystal or ceramic resonator oscillator circuits that are utilized to provide the units with accurate timing signals which permit the units to communicate asynchronously when primary AC power is absent. These internal timing circuits also provide the carrier frequency used for power line communication.
Additional objects and advantages of the present invention will become apparent from a reading of the following detailed description of the preferred embodiment which makes reference to the accompanying drawings in which: